<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<script>
    function f(n) {
        n = n -0;
        if(n ===1 ){
            return 1
        }
        else if(n ===2 ){
            return 2
        }else{
            return f(n-1) + f(n-2)
        }
    }

    let res = f(100);

    document.write(res)

</script>

</body>
</html>